This study will enroll up to 360 women with brain metastases from breast cancer, and will evaluate if whole brain radiation therapy given with RSR13 will have a better treatment effect than whole brain radiation therapy alone. RSR13 will be infused intravenously (IV) through a central catheter placed in a central vein. Women randomized (assigned) to receive RSR13, therefore, will need to have a central catheter placed for treatment unless one is already in place.